Method for dispensing sample liquid and pipette for dispensing sample liquid

Abstract

A method for dispensing a sample liquid including evaluating a pressure signal from the tip pressure sensor with the control device to obtain a working fluid pressure, evaluating a flow signal from the flow sensor arrangement with the control device to obtain a sample liquid flow rate, changing a pressure for working fluid received in the pipette tip holder with the working fluid device according to a first curve for the working fluid pressure, so that sample liquid passes through a dispensing opening of the pipette tip spaced apart from the pipette tip holder, determining a flow resistance characteristic value for the sample liquid, taking into account the working fluid pressure and the sample liquid flow rate, and then changing the pressure for the working fluid received in the pipette tip holder again using the working fluid device according to a second working fluid pressure curve.

1 . A method for dispensing a sample liquid, with a pipette comprising a working fluid device, a flow sensor arrangement, a pipette tip holder, a pipette tip that can be filled with sample liquid, a tip pressure sensor arranged on the pipette tip holder, and a control device, comprising the steps of:
 evaluating a pressure signal from the tip pressure sensor with the control device to obtain a working fluid pressure,   evaluating a flow signal from the flow sensor arrangement with the control device to obtain a sample liquid flow rate,   changing a pressure for working fluid received in the pipette tip holder with the working fluid device according to a first curve for the working fluid pressure, so that sample liquid passes through a dispensing opening of the pipette tip spaced apart from the pipette tip holder,   determining a flow resistance characteristic value for the sample liquid, taking into account the working fluid pressure and the sample liquid flow rate, and then again changing the pressure for the working fluid received in the pipette tip holder with the working fluid device according to a second curve for the working fluid pressure, wherein the second curve for the working fluid pressure is determined taking into account the flow resistance characteristic value so that a predetermined sample liquid quantity passes through the dosing opening.   
     
     
         2 . The method according to  claim 1 , wherein the again change in pressure for the working fluid received in the pipette tip holder is controlled. 
     
     
         3 . The method according to  claim 1 , wherein the flow sensor arrangement is designed as a soft sensor arrangement and determines the flow signal on the basis of at least one pressure signal from a pressure sensor assigned to the working fluid device. 
     
     
         4 . The method according to  claim 3 , wherein the working fluid device has a positive pressure source and/or a negative pressure source, wherein a positive pressure sensor is associated with the positive pressure source and/or a negative pressure sensor is associated with the negative pressure source, wherein the flow sensor arrangement determines the flow signal on the basis of a pressure signal from the positive pressure sensor and/or a pressure signal from the negative pressure sensor and the pressure signal from the tip pressure sensor. 
     
     
         5 . The method according to  claim 1 , wherein the working fluid device has a piston and the pipette tip holder is designed as a cylinder in which the piston is guided, wherein the flow sensor arrangement is designed as a soft sensor arrangement and determines the flow signal on the basis of a displacement signal from a displacement sensor assigned to the piston and the pressure signal from the tip pressure sensor. 
     
     
         6 . The method according to  claim 1 , wherein, when determining the flow resistance characteristic value, a simulated control is performed, in which the working fluid pressure is used as the input and the sample liquid flow rate is used as the reference variable, and a simulated sample liquid flow rate is determined by means of a simulation, wherein the simulated sample liquid flow rate is used as a control variable of the simulated control. 
     
     
         7 . The method according to  claim 6 , wherein the sample liquid flow rate is used as a reference variable of the simulated control, wherein the simulated sample liquid flow rate is used as a measured variable of the simulated control, which is fed back to the sample liquid flow rate used as a reference variable of the simulated control. 
     
     
         8 . The method according to  claim 7 , wherein a control deviation of the simulated control is determined as a difference between the sample liquid flow rate used as a reference variable of the simulated control and the simulated sample liquid flow rate used as a measured variable of the simulated control used as a measured variable of the simulated control, wherein the control deviation of the simulated control is fed to a disturbance model of the simulated control, wherein the disturbance model of the simulated control is designed as a function with which a preliminary flow resistance characteristic value is determined, wherein the preliminary flow resistance characteristic value is used as a parameter of the simulated control. 
     
     
         9 . A pipette for dispensing a sample liquid, comprising a working fluid device, a flow sensor arrangement, a pipette tip holder, a pipette tip that can be filled with sample liquid, a tip pressure sensor arranged on the pipette tip holder, and a control device, wherein the control device is designed to execute a method according to  claim 1 .